Enhancing the static stability of older adults: A study on foot sole vibration intensities and locations

Background
Falls are a major public health concern for older adults, driven by age-related declines in somatosensory feedback which is critical for postural stability. Plantar vibratory stimulation may enhance balance, yet the optimal parameters remain unclear.

Research question
How may different foot sole vibration intensities and locations improve static stability in older adults?

Methods
Eighteen healthy older adults (aged 66.6 ± 3.1 years) received mechanical vibrations at 0 %, 90 %, and 130 % of their sensory threshold, applied to the forefoot & heel (F&H) and midfoot (MF) of both feet, in eyes-open (EO) and eyes-closed (EC) conditions. Static stability was assessed using center of pressure (COP) metrics, including sway velocity, average sway amplitude, and sway area in the anterior-posterior (AP) and mediolateral (ML) directions.

Results
Compared to 0 %, both 90 % and 130 % intensities significantly reduced total sway velocity, AP sway velocity, ML sway velocity, and AP sway amplitude (p < 0.05) in the EO condition. In the EC condition, these effects persisted (p < 0.05), with the additional benefits of reduced ML sway amplitude and total sway area (p < 0.05), and no consistent differences between locations (F&H vs. MF).

Significance
Moderate vibration intensities enhance static stability across different foot sole locations, suggesting that footwear and insoles incorporating vibration may serve as potential strategies for fall prevention among older adults.